Brain structural anatomy in familial schizophrenia was studied with magnetic resonance imaging (MRI). MRI scans of 25 schizophrenic siblings from 14 unrelated families, 8 of their nonpsychotic siblings, and 20 controls were analyzed. Volume estimates were made of the cerebrum, temporal lobes, amygdala-hippocampus, amygdala-hippocampus plus parahippocampal gyrus, caudate, lentricular nucleus, lateral ventricles, and third ventricle. Compared with the control sample the schizophrenic siblings had significant volume reduction of the temporal lobes, bilaterally, and significant increase in ventricular brain ratio (VBR). These structural abnormalities may be part of the pathophysiology of the disease.